EFFECTS OF EXERCISE ON PLASMA-LIPIDS AND METABOLISM OF LACTATING WOMEN

To examine the effects of exercise on plasma lipids and metabolism dur ing lactation, sedentary, exclusively breast-feeding women were random ly assigned to an exercise (E) or control (C) group at 6-8 wk postpart um. E subjects performed aerobic exercise 45 min.d(-1), 5 d.wk(-1), fo r 12 wk. Resting metabolic rate (RMR), energy expenditure, body compos ition, and dietary intake were measured at 6-8, 12-14, and 18-20 wk po stpartum. Maximum oxygen uptake (VO2max), postprandial insulin, glucos e, and thermic response, and plasma lipid levels were measured at 6-8 and 18-20 wk. VO2max increased by 25% vs 5% in the E vs the C group, r espectively (P < 0.0001). RMR was similar between groups and did not c hange over time. Weight and percent body fat declined (P < 0.01) durin g the study, but there was no difference between E and C groups. Exerc ise marginally increased high-density lipoprotein cholesterol levels ( P < 0.08), but did not affect other lipid concentrations. Insulin resp onse decreased as VO2max increased (P = 0.05). There was no effect of time or group on glucose or thermic response. Exercise improves cardio vascular fitness during lactation, but does not increase the rate of p ostpartum weight loss.